<%@ page import="java.util.ArrayList" %>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <meta charset="utf-8">
    <title>Title</title>
</head>
<body>
<%
    request.setAttribute("str", null);
    request.setAttribute("str1", "");
    request.setAttribute("str2", " ");
    request.setAttribute("list", new ArrayList<>());
%>
${empty str} true
${empty str1} true
${empty str2} false

${empty list} true

${empty str ? "空/null" : str}
</body>
</html>
